error loading main page

POST /filevistacontrol/filevista.asmx/GetLanguageFile

Returns this in fiddler
<?xml version="1.0" encoding="utf-8"?>
<Result error="0" message="Session has expired." command="RefreshPage" />

and gives an error in javascript.  

I have no idea why this is a problem.  It's set for InProc sessions in web.config.  I tried to set it for StateServer and it complained that the object wasn't marked serializable so I couldn't use that.

... ?

Do you see if the ASP.NET cookie is sent with the post in Fiddler? You should see something like that in cookie header:

ASP.NET_SessionId=iy0ol345fjwmzg45y030hj45

Also find the earlier login request in fiddler (POST /administration.asmx/LoginUser) and see if the cookie is set with same value in response header:

Set-Cookie: ASP.NET_SessionId=iy0ol345fjwmzg45y030hj45; path=/; HttpOnly

If these are missing, please make sure cookies are enabled (for your url) in your browser.